In certain medical procedures, for example, colonoscopy, radiographic examination and in preparation for patients undergoing bowel surgery, it is often critical that the colon be emptied as completely as possible. For example, in order to obtain satisfactory radiographs it is often essential that the intestines be cleansed sufficiently, particularly with regard to the elimination of gas from the colon. The same condition also applies when the colon is preoperatively prepared for surgery, or for diagnostic procedures such as colonoscopies, in which case it is also necessary to remove fecal waste materials.
Typical prior art colonic purgative procedures involved the emptying of the colon using water enemas wherein large quantities of water are introduced into the colon to induce emptying--the contents of the colon being expelled in the form of a suspension. It has, however, been recognized that the use of enemas may be injurious to the patient. In view of the hazard and disadvantages associated with large volume water enemas, an alternative has been to introduce enemas of a hypertonic aqueous solution typically, of various salts to substitute for the large water enema. The advantage of these salt formulations is that they require significantly less water volume in their administration. The effect of these hypertonic enemas is based on the increase of the osmotic pressure in the colon which, in turn, may have undesirable side effects, particularly, if the hypertonic solution diffuses through the wall of the colon and disturbs the fluid balance of the body. Although this is an improvement over simple water enemas, this potential side effect limits the utility of these compositions.
Additionally, many enema compositions in aqueous solutions include a contact laxative agent causing peristalsis in the colon with sufficient concentration of laxation without the need for excessive amounts of water. Such compositions often include salt mixtures and may also contain chemical agents such as propylene glycol and non-ionic wetting agents such as polyether alcohols. The problems with these formulations, aside from the often problematic methods of enema administration, are incomplete evacuation of the bowels, repeat administrations and the inclusion of certain chemicals which may have an irritating effect on the colonic walls. Furthermore, because it is often necessary to employ repeated washout enemas to clear the colon effectively, the potential for such chemical irritation is greatly increased.
More recently, a number of orally administered liquid pharmaceutical compositions have been developed for use as gastrointestinal washes for diagnostic purposes or for use as cathartic laxatives. Such preparations consist of aqueous solutions of polyethylene glycol and electrolytes suchs as sodium sulfate, sodium bicarbonate, sodium chloride and potassium chloride. These orally administered compositions are particularly useful in the rapid washing of the colon for diagnostic purposes. For example, when a powerful gastrointestinal wash is required, such preparations are generally administered in a quantity of about four liters, the composition being typically formulated according to the following: polyethylene glycol 59 g., sodium sulphate 5.68 g., sodium bicarbonate 1.69 g., sodium chloride 1.46 g., potassium chloride 0.745 g. and water to make up one liter. Laxation and relatively thorough evacuation is often significantly improved over enema formulations, and generally without the problems often encountered with enema administrations.
The advantages of using these preparations over other orally administered preparations are a drastic reduction in wash time (from 3-2 days to 4-5 hours) and the minimization of water and electrolyte losses. The advantages which these types of solutions provide are derived from two essential characteristics of the preparation, namely, its isoosmoticity with the physiological liquids, and the balance of the ion species in solution, so as to compensate the transport mechanisms which regulate gastrointestinal absorption. These characteristics result in substantial isotonicity between the preparation and the intracellular and extracellular fluids at the tissues of the digestive tubes walls.
Commercially available products embodying these formulations typically utilize a polyethylene glycol formula serving as a non-absorbable osmotic agent with a mixture of electrolytes for replenishment, so that patients do not become dehydrated. Patients are required to ingest a significant amount of volume for purgation which may include a one eight ounce glass every ten minutes for a total of one gallon of fluid. Due to the fact that the volume is so high, use of this type of formulation is frequently associated with distention and nausea on a significant scale.
Another serious drawback of these known preparations is their unpleasant, bitter, saline taste which in the more sensitive patients can lead to vomiting--thereby preventing ingestion. However, as the requirement of solution isotonicity is necessary to obtain the aforesaid advantages, the introduction of water soluble adjuvants, for example, to alter taste, must be avoided. Even the most common natural sweeteners such as glucose, fructose, saccharose, and sorbitol could change the osmolarity of these solutions and the inclusion of such adjuvants are generally expressly prohibited. Moreover, even altering the unpleasant taste of these preparations with artificial sweeteners or flavorants in these commercial preparations must be avoided as they could also alter the critical isotonicity.
Furthermore, in the aforesaid preparations of the known art, it is also well recognized that the addition of appreciable quantities of substances which can be fermented by the intestinal flora should be avoided. This is because gas could form which could be extremely dangerous in the case of colonoscopy with electrocautery.
In an attempt to avoid the problems associated with the high volume types of preparations, other investigators have utilized ingestible preparations which consist of aqueous solutions of phosphate salts. The aqueous phosphate salt solution produces a tremendous osmotic effect on the intra-luminal contents of the bowel and therefore, evacuation of the bowel occurs with a tremendous increase in the influx of water and electrolytes into the colon. This has been developed for the express purpose of decreasing the volume required in colonic purgations. One such preparation basically is comprised of 480 grams per liter monobasic sodium phosphate and 180 grams per liter dibasic sodium phosphate in stabilized buffered aqueous solution and is sold under the brand name Fleets Phospho-Soda.TM.. Patients are typically required to take two three ounce dosages of this preparation, separated by a three hour interval for a total of six ounces, which is a significant reduction compared to large volumes required by other high volume preparations.
The major short-coming of such concentrated aqueous phosphate solution administration is that the aqueous solution is extremely unpalatable, so much so that the recommended dosage form is administered ice cold so as to minimize the objectionable saline taste. Often, patients complain of severe nausea and vomiting, secondary to the extremely salty taste of the preparation. Frequently, patients cannot even tolerate the ingestion of this preparation at the initial dose and often the second dose becomes even more problematic due to the unpalatable extremely salty taste, even when the taste is partially masked by the use of flavoring agents. Thus, while concentrated purgation solutions represent a slight improvement over other methods of inducing purgation, the short comings of these solutions are readily apparent.
From the foregoing, it can be seen that it is desirable to have an orally administered colonic purgative formulation which may be easily and conveniently administered and which avoids the problems and objectionable tastes of known formulations. It can also be seen that it is desirable to have such a purgative formulation which may be administered without large volumes of water necessary in conventional formulations and which avoids other potentially irritant chemicals or chemicals which could effect osmolality.
It is an object of the present invention to provide easily and conveniently administered dosage formulations of effective colonic purgatives.
It is yet another object of the present invention to provide a colonic purgative formulation which provide purgative activity at lower dosages of salt than prior art sodium phosphate tablets.
It is still another object of the present invention to provide a method of administering a colonic purgative with a minimum amount of patient discomfort.
Yet another object of theinstant invention is to provide a formulation for colonic purgatives which avoids the addition of other components which may be broken down by intestinal flora.
These and other objects and advantages of the invention will be evident after reading the following description.